The mass of the stoichiometric reactant mixture is

yields 2677 kJ of energy.
The mass of the stoichiometric reactant mixture is:
!
"
#
$
%
&
’ +
!
"
#
$
%
&
’
mol
g 49 . 117
mol 3
mol
g 98 . 26
mol 3
= 433.41 g
For 1.000 kg of fuel: 1.000 × 10
3
g ×
g 41 . 433
kJ 2677 !
= − 6177 kJ
In Exercise 71, we get 4594 kJ of energy from 5 mol of N
2
O
4
and 4 mol of N
2
H
3
CH
3
.
The mass is:
!
"
#
$
%
&
’ +
!
"
#
$
%
&
’
mol
g 08 . 46
mol 4
mol
g 02 . 92
mol 5 = 644.42 kJ
For 1.000 kg of fuel: 1.000 × 10
3
g ×
g 42 . 644
kJ 4594 !
= − 7129 kJ
Thus we get more energy per kilogram from the N
2
O
4
/N
2
H
3
CH
3
mixture.
74. a. C
2
H
4
(g) + O
3
(g) → CH
3
CHO(g) + O
2
(g) Δ H° = − 166 kJ − (143 kJ + 52 kJ)
= − 361 kJ
b. O
3
(g) + NO(g) → NO
2
(g) + O
2
(g) Δ H° = 34 kJ − (90. kJ + 143 kJ)
= − 199 kJ
c. SO
3
(g) + H
2
O(l) → H
2
SO
4
(aq) Δ H° = − 909 kJ − [ − 396 kJ + (-286 kJ)]
= − 227 kJ
d. 2 NO(g) + O
2
(g) → 2 NO
2
(g) Δ H° = 2(34) kJ − 2(90.) kJ = − 112 kJ

CHAPTER 9 ENERGY, ENTHALPY, AND THERMOCHEMISTRY
374 Even-numbered Problem Solutions
o
f
o
×
5
8

CHAPTER 9 ENERGY, ENTHALPY, AND THERMOCHEMISTRY
375 Even-numbered Problem Solutions
Additional Exercises
− Δ (PV)
3
kJ
!
!

CHAPTER 9 ENERGY, ENTHALPY, AND THERMOCHEMISTRY
376 Even-numbered Problem Solutions